[cups.general] CUPS 1.4.4 slow - problem checklist?
Tim Waugh
twaugh at redhat.com
Tue Oct 19 07:35:15 PDT 2010
On Tue, 2010-10-19 at 06:28 -0700, John A. Murdie wrote:
> Tim, thank you - having discovered that you were a co-author of the
> code I was going to e-mail you after some more investigation of what
> was going on. Here might be as good a place as any to discuss the
> matter, though we can take it out of this forum if you prefer or if it
> gets too detailed, or becomes off-topic. (For all I know, this might
> be a CUPS 1.4.4 problem.)
Might be better on system-config-printer-devel:
https://fedorahosted.org/mailman/listinfo/system-config-printer-devel
> I am very grateful for your assistance. I'm particularly worried that
> system-config-printer-applet seems to poll CUPS whenever PyGTK is idle
> using gobject.idle_add() rather than using gobject.timeout_add() with
> a few seconds between polls; is that a concern?
The idle_add() callback repeats until the user function returns False,
just as with timeout_add().
The applet listens for D-Bus signals from CUPS and schedules an
IPP-Get-Notifications request whenever it hears one. This is deferred
by 200ms (and reset on each signal) to make sure we only issue one
request whenever lots of signals occur in quick succession.
If D-Bus signals are not available, it uses the notify-get-interval
specified by the CUPS scheduler.
> <monitor.Monitor instance at 0x9b13eec>: CUPS IPP error (1025, 'client-error-forbidden')
> Created subscription -1
This looks like IPP-Create-Subscription is not allowed for this client,
due to the way CUPS is configured. Subscriptions are more efficient for
this sort of application because it can be told about relevant changes
rather than having to fetch the entire list each time:
> <monitor.Monitor instance at 0x9b13eec>: printers and jobs lists provided
But how often is it doing that? Does it happen continuously even when
there is no activity, or does it only happen whenever there is some
change in the status of a job?
Tim.
*/
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